It is well known in motor vehicles to provide an air bag module including an inflatable air bag which deploys into the vehicle interior for protection of one or more vehicle occupants. The air bag module includes an air bag deployable in a generally rearward direction towards the vehicle passenger. It is known to mount the air bag module beneath the instrument panel cover and to provide an air bag deployment opening in the instrument panel cover through which the air bag may deploy. The deployment opening in the instrument panel cover is typically closed by a separate air bag cover door which opens in response to air bag deployment to permit the air bag to deploy into the passenger compartment in a generally rearward direction.
The air bag cover door conceals the air bag module from view and is supported on the instrument panel in a manner which will protect the air bag module and yet open rapidly in the event of air bag deployment. The prior art has provided many such air bag door constructions for closing the deployment opening in the instrument panel cover. For example, the deployment opening is generally provided with a separate cover door having color and texture for generally matching that of the instrument panel front of dash. However, the separate cover door is typically not made of the same material as the instrument panel and some variations in color and texture will occur. Furthermore, the outline of the deployment door opening and the cover is visible on the instrument panel directly in front of the passenger. In addition, weakened seams or tear lines are typically provided which break open upon air bag deployment and may also be visible to the passenger.
Thus, it has also been suggested to provide thinned sections in the instrument panel such that the deployment opening is only partially formed until the inflating air bag forces open the deployment door to provide the deployment opening. The typical instrument panel cover includes an underlying generally rigid substrate made of a molded plastic material and covered by foam and skin. The scoring or cutting may be accomplished by using cutting blades or water jets. However, difficulty arises in controlling the depth of the cuts and assuring that the cuts only extend partially through the substrate. Currently, it is difficult to use lightweight rigid materials for the substrate since the overlying soft layers can be easily damaged during manufacturing when attempting to sever the strong substrate.